What term describes gaps in rock sequences caused by missing rock layers?

What term describes gaps in rock sequences caused by missing rock layers?

• A. Bedding planes
• B. Erosional surfaces
• C. Unconformities
• D. Intrusions

Answer: (C)

Gaps in the rock record where time and some rock material are missing are called unconformities. They show up when deposition pauses for a long period or when existing rocks are eroded away, so younger layers sit directly on much older ones with a break in the sequence. Bedding planes are simply the surfaces between layers formed during regular deposition and don’t by themselves indicate a time gap. An erosional surface can be part of an unconformity, but it’s the hiatus in time that defines the term. Intrusions are molten rock that cuts across existing layers, which disrupts the sequence but doesn’t describe a missing interval in the record.

Gaps in the rock record where time and some rock material are missing are called unconformities. They show up when deposition pauses for a long period or when existing rocks are eroded away, so younger layers sit directly on much older ones with a break in the sequence. Bedding planes are simply the surfaces between layers formed during regular deposition and don’t by themselves indicate a time gap. An erosional surface can be part of an unconformity, but it’s the hiatus in time that defines the term. Intrusions are molten rock that cuts across existing layers, which disrupts the sequence but doesn’t describe a missing interval in the record.